Sita Bauelemente GmbH/UK
Roof Drainage - Long Distance Planning
A 28,500 m² roof area but only one side of
the building on which fall pipes could be
installed. That was the special challenge
posed for draining the flat roof on Carl
Durach GmbH & Co. KG's new building at
Todtenweis in Bavaria. A siphonic drainage
system guides the rainwater smoothly
over the enormous roof into an infiltration
structure and a soak away trench.
Archetech - Issue 20 [Page 62]
From a roof area of 30,000 m² extended to
55,600 m² - that is a fair description of the
current development at Carl Durach GmbH
& Co. KG. The new build which was erected
alongside an existing building 130 m in
length on the company's site is designed
to replace outdoor facilities which were
previously rented. Since part of the current
warehouse buildings is being converted,
this created the need for additional space.
Another aim was to modernise the entire
logistics system. The latest e xtension now
enables the majority of goods to be prepared
and palletised ready for shipment from the
production plant to dealers.
The developer did not want any underground
pipes under the new building, in particular
because there is an existing infiltration
structure under the new building and the
site also suffers from an unfortunate ground
water level. The total volume of rain of over
720 litres per second in the main drainage
system should be drained into the infiltration
structure on the existing building and in a
soak away trench located on the western side
of the large company site.
In view of the building's size of 160 x 160 m,
therefore, individual rainwater sections of up
to approx. 180 m were required before the
water could be redirected from horizontal to
vertical. This could only be achieved using a
siphonic drainage system which, in contrast
to a conventional system, does not need
pipework installed to a gradient.
Drainage in the "green area"
The Kostra catalogue of the German
Meteorological Service does not contain any
special features for the town of Todtenweis.
With annual rainfall of 310 l/s*hectare and
once in a century rainfall of 584 l/s*hectare,
the town is very average for the region.
The main drainage system comprises 90
DN 70 SitaDSS Profi outlets which remove
approximately 720 litres per second from the
roof. They were also fitted with Sita retaining
units to extend over the 12 cm think thermal
insulation. 58 outlets of the same type were
used for the emergency drainage system,
once again fitted with Sita retaining units. If
the emergency drainage system is activated
by heavy rain, the emergency drainage
lines, which can be identified by the yellow
Sita retaining units, can remove up to an
additional 440 litres per second on to areas
on the outsides of the building which are
freely submersible.
A total of 3300 m of PE pipes are
interconnected under the roof area of the
new building, which measures approx. 25600
m² and is connected to the 2900 m² existing
roof, to form a complex drainage system.
Whilst the emergency drainage system
drains the water freely on to the site, the
main drainage system feeds the rainwater
through partly exterior ground pipes into
the company's own infiltration structures
and soak away systems - without adding
any rainwater to the public sewers. Since all
the water drained off the building runs to
its western side, some enormous pipeline
lengths were required. The installation of the
various PE pipelines for the siphonic system,
which are up to 180 m in length, required
genuine long distance planning between
the building contractors. A combination of
the SitaDSS rapid installation system and
the structure fastening systems supplied
by Dietul based in Kehlheim hold the long
distance siphonic pipeline system securely up
to the points at which it transfers the water
into the ground pipes because when the
water flows into the pipe due to the vacuum,
siphonic drainage systems tend to developed
their own dynamic forces . To prevent this the
horizontal pipes were fixed every 6.6 m to a
rail on the concrete trusses using integrated
channels. This inhibits the pipes extending in
length due to heat and sagging, whilst any
movement of the siphonic drainage system
will be safely absorbed by the retaining
construction.
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